A so-called back-illuminated semiconductor photodetecting device has been known conventionally as a semiconductor device. This type of semiconductor device has a semiconductor substrate and has a photodetecting unit on one surface of the semiconductor substrate. A portion of the semiconductor substrate on the side opposite the photodetecting unit is trimmed to form a recessed portion in the semiconductor substrate. A thinned portion is thus provided at the portion of the semiconductor substrate at which the photodetecting unit is disposed. This thinned portion is provided to accommodate ultraviolet rays, soft X-rays, electronic beams, and other energy rays that will be absorbed and cannot be detected at high sensitivity by a thick semiconductor substrate. At this thinned portion, light that is made incident on the surface at the recessed portion side of the semiconductor substrate is detected by the photodetecting unit.
As an example of a back-illuminated semiconductor device, there is a semiconductor device that has a BT-CCD (back-thinned CCD). The BT-CCD is used as a detecting unit of a semiconductor inspecting device. An example of a conventional semiconductor device having a BT-CCD is described in Patent Document 1.
FIG. 12 is a sectional view of an arrangement of the semiconductor device described in Patent Document 1. As shown in FIG. 12, a P-type silicon layer 104, which is a semiconductor substrate having a CCD 103 on a surface that opposes a wiring substrate 102, is mounted via metal bumps 105 onto wiring substrate 102, which is fixed to a bottom portion of the interior of a package 101. Each wiring 106 on wiring substrate 102 is connected at one end to a metal bump 105 and has a bonding pad (not shown) for externally taking out detected signals at the other end, and each bonding pad is electrically connected by a bonding wire 107 to a lead terminal (not shown) of package 101. Furthermore, a gap between wiring substrate 102 and P-type silicon layer 104 is filled with an underfill resin 108 for reinforcing the bonding strengths of metal bumps 105.    Patent Document 1: Japanese Published Unexamined Patent Application No. Hei 6-196680
However, when the underfill resin fills the gap between the wiring substrate and the thinned portion of the semiconductor substrate as shown in FIG. 12, the thinned portion may crack due to the stress that arises due to a thermal expansion coefficient difference between the underfill resin and the semiconductor substrate in the process of heating or cooling to cure the underfill resin. Even if cracking does not occur, the thinned portion may become distorted by being pulled by the contraction of underfill resin. Such distortion of the thinned portion of the semiconductor substrate may bring about adverse effects on focusing with respect to the photodetecting unit and uniformity and stability of sensitivity of the photodetecting unit during use of the semiconductor device.
This invention was made to resolve the above issue and an object thereof is to provide a semiconductor device, with which the distortion and cracking of a thinned portion of a semiconductor substrate are prevented to enable high precision focusing with respect to a photodetecting unit and uniformity and stability of high sensitivity of the photodetecting unit to be maintained.